Experimental evaluation of critical resolved shear stress for the first-order pyramidal c plus a slip in commercially pure Ti by micropillar compression method

The plastic deformation behavior of commercially pure Ti single crystals has been investigated by uniaxial micropillar compression tests as a function of crystal orientation and specimen size at room temperature. {10 (1) over bar1} (first-order) pyramidal c+a slip and prism a slip are activated in micropillar specimens with the [0001] and [2 (1) over bar(1) over bar0] orientations, respectively. {10 (1) over bar1} pyramidal c+a slip has never been observed to operate as a major deformation mode in compression tests of 'bulk' single crystals at room temperature, in which {11 (2) over bar2}<11<(2)over bar>(3) over bar> twinning is usually observed. The CRSS values for {10 (1) over bar1} pyramidal c+a slip and prism a slip increase with the decrease in the specimen size, following an inverse power-law relationship with a power-law exponent of about 0.06 and 0.59, respectively. The extrapolation of the inverse power-law relationship up to the 'bulk' specimen size estimated from the CRSS values of prism a slip gives the 'bulk' CRSS value for {10 (1) over bar1} pyramidal c+a slip to be 580-635 MPa, which is by far higher than those for any other deformation modes operative at room temperature. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.